# Qalsody (tofersen) by Biogen

Canonical page: https://technooptimist.io/biotech/qalsody
Frontier: [Biotech](https://technooptimist.io/biotech.md) · Field: RNAi & antisense drugs · Company: [Biogen](https://technooptimist.io/companies/biogen.md)
Stage: Deploy (4 of 5: Research → Proto → Pilot → Deploy → Scaling)
Updated: last update 2024-05-01, facts checked 2026-10-11
Goal: Slow or stop ALS caused by SOD1 mutations by switching off the toxic gene in the brain and spinal cord, and ultimately prevent the disease by treating carriers before symptoms start.
Status: Approved in the US (2023) and EU (2024); ATLAS trial in presymptomatic SOD1 carriers ongoing.
Next milestone: ATLAS: treat presymptomatic SOD1 carriers when neurofilament rises

## Milestones

| Status | Milestone | Date | Slip |
| --- | --- | --- | --- |
| Done | VALOR phase 3: neurofilament down 55%, function missed significance |   |   |
| Done | FDA accelerated approval for SOD1-ALS | 25 Apr 2023 |   |
| Done | EU approval under exceptional circumstances | May 2024 |   |
| Current | ATLAS: treat presymptomatic SOD1 carriers when neurofilament rises |   |   |

## Most important updates

- **May 2024**: EU approves Qalsody for SOD1-ALS under exceptional circumstances. The European Commission authorised tofersen for adults with SOD1-ALS, the first EU treatment aimed at a genetic cause of ALS. ([our story](https://technooptimist.io/stories/eu-approves-qalsody-for-sod1-als-under-exceptional-circumstances-cfea268a.md) · [original source](https://www.europeanpharmaceuticalreview.com/news/229724/oligonucleotide-als-therapy-approved-in-eu/))
- **25 Apr 2023**: FDA grants accelerated approval to Qalsody, the first treatment targeting a genetic cause of ALS. The FDA approved tofersen (Qalsody) for adults with ALS caused by SOD1 mutations, based on a drop in neurofilament light, a blood marker of nerve damage. ([our story](https://technooptimist.io/stories/fda-grants-accelerated-approval-to-qalsody-the-first-treatment-8e3330b4.md) · [original source](https://www.sec.gov/Archives/edgar/data/874015/000114036123020335/brhc20051944_ex99-1.htm))

## Current obstacles

- **Clinical benefit still being confirmed**: VALOR's 28-week function score missed significance; approval rests on neurofilament until ATLAS confirms benefit.
- **Repeated spinal injections**: Lifelong lumbar punctures every 4 weeks are a burden and carry side effects like headache and back pain.

## Physics limits

- **Dead motor neurons don't come back**: Silencing the gene can stop further damage but cannot regrow lost neurons, so benefit depends on treating early, ideally before symptoms.
- **One gene, few patients**: Each antisense drug fixes one gene; SOD1 explains only about 2% of ALS, and most cases have no single known genetic cause to target.

## How it works

### Antisense: A strand that matches SOD1's message

A short, chemically armoured DNA-like strand pairs with SOD1 messenger RNA and marks it for destruction.

### Delivery: Injected into spinal fluid

Given by lumbar puncture so it bathes the spinal cord and brain, which a drug in the blood can't reach.

### Effect: Less toxic protein

Mutant SOD1 misfolds and poisons motor neurons; lowering it slows nerve damage, seen as falling neurofilament.

### Prevention: Treat before symptoms

Carriers' neurofilament rises months before weakness; ATLAS starts treatment at that signal.

## Spec sheet

| Spec | Qalsody (tofersen) | Provenance |
| --- | --- | --- |
| Plasma neurofilament change (28 wk) | -55% vs +12% on placebo | reported |
| Spinal-fluid SOD1 protein | -35% vs -2% on placebo | reported |
| SOD1-ALS patients in the US | ~330 (about 2% of ALS) | reported |
| Dosing | 3 loading doses 14 days apart, then every 28 days | reported |
| VALOR trial size | 108 patients | reported |

Provenance: reported = stated by the company; estimated = our estimate; sample = a sample figure.

## About Biogen

US neuroscience drugmaker. It licensed tofersen from Ionis and sells it as Qalsody, the first drug that targets a genetic cause of ALS.

- Qalsody: FDA accelerated approval April 2023, EU approval May 2024, for ALS caused by SOD1 mutations.
- ATLAS phase 3 tests whether starting tofersen before symptoms can delay or prevent ALS.

- Headquarters: US
- Status: public
- Website: https://www.biogen.com
- Partners, customers, investors: Ionis Pharmaceuticals (partner)

Company page: https://technooptimist.io/companies/biogen.md

## Related programs

Everything in Biotech: https://technooptimist.io/biotech.md

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